The officers, who joined in a recruitment boom in the 1970s following improvements in pay and conditions, will be eligible to leave after completing 30 years service.

Police chiefs are now looking at a number of initiatives to plug the gap, allowing key workers to stay on and also piloting an in-house employment agency for retired officers to fill vacancies on a short or medium term contracts.

The issue is particularly pressing as police assess the impact of providing security for the 2012 Olympic Games in London.

A report before the ruling Police Authority’s Personnel Committee today also identified analysts and forensics specialists, such as fingerprint experts and scenes of crime officers, as key civilian posts which could face staffing problems if measures were not introduced.

The report said officers who joined the force in the 1970s would soon have the option to retire.

“This means that the force could potentially lose up to 2,000 officers in the period running up to 2011/12,” the document said.

In the past four years, 1,900 officers have retired from the force after reaching 30 years service, forcing recruiters to work overtime to plug the gap, bringing in more than 1,570 front line personnel in the past two years and swelling the ranks to 8,561 officers.

The report said a number of measure were in place and being developed.

Almost 100 retired officers are taking part in the 30+ scheme, which allows officers with key skills to stay on.

More than 100 officers are also registered with an in-house staff agency. The force is also looking at panels to identify key people to keep or promote.

One key area is the number of PCSOs who use the job as a stepping stone to becoming a bobby. Almost 200 have joined the ranks alongside more than 100 civilian police staff.

The report concludes: “Recent work has delivered more flexibility within the workforce.

“Further work on the retention of officers and the identification of opportunities for them to be engaged in other non-warranted activities is needed.

“In addition we will need to introduce measures to increase the force’s skill base, particularly in certain operational skills, to address the profile of officer retirements.”